Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Angiotensin-converting enzyme (ACE) activity in the intestinal whole homogenate was showed as three peaks on a column of Sephacryl S-300 HR gel filteration. Over 90% of total ACE activity was found in a soluble fraction separated with an ultracentrifuge of the intestinal homogenate, and the ACE activities were detected as two peaks on the same column. On the other hand, two peaks of ACE activities were found in a membrane-bound fraction of treated with trypsin on the Sephacryl column and confirmed with the two peaks of the soluble fraction, while the fraction extracted with Triton X-100 of the membrane-bound fraction showed only one peak as major peak. All ACE peaks were inhibited by addition of EDTA or captopril and by absence of chloride ion completely. We purified one ACE from the soluble fraction by lisinopril-linked Sepharose 6B affinity column chromatography and Cellulofine GCL-200 gel filteration. This enzyme was a 1323-fold purification and its final recovery was 25%. The molecular weight of this enzyme (180,000) was larger than that of ACE from human kidney (170,000), estimated by 7.5% SDS-PAGE. The Km value of the enzyme for HHL was 2.1 mM. The enzyme activity was competitively inhibited by captopril.
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PMID:Purification of angiotensin-converting enzyme from human intestine. 255 10

Functional rat or human asialoglycoprotein receptors (ASGP-Rs) are hetero-oligomeric integral membrane glycoproteins. Rat ASGP-R contains three subunits, designated rat hepatic lectins (RHL) 1, 2, and 3; human ASGP-R contains two subunits, HHL1 and HHL2. Both receptors are covalently modified by fatty acylation (Zeng, F.-Y., Kaphalia, B. S., Ansari, G. A. S., and Weigel, P. H. (1995) J. Biol. Chem. 270, 21382-21387; Zeng, F.-Y., Oka, J. A., and Weigel, P. H. (1996) Biochem. Biophys. Res. Commun. 218, 325-330). We report here that the single Cys residue in the cytoplasmic domain of each RHL or HHL subunit is fatty acylated. The degree of acylation is >/=90% per subunit. Deacylation of affinity-purified ASGP-Rs with hydroxylamine results in the spontaneous formation of dimers through reversible disulfide bonds, indicating that deacylation concomitantly generates free thiol groups. Reaction of hydroxylamine-treated ASGP-R with [14C]iodoacetamide resulted in the specific incorporation of radioactivity into all RHL and HHL subunits, verifying that fatty acids are attached via thioester linkages. To identify the Cys residue involved in the thioester linkages, 14C-carboxyamidomethylated RHL subunits were separated by SDS-polyacrylamide gel electrophoresis and digested in-gel with trypsin, and the resulting peptides were separated by reverse-phase high performance liquid chromatography. Amino acid sequence of radioactive peptides revealed that Cys35 in RHL1 and Cys54 in RHL2 and RHL3 were radiolabeled and, therefore, are fatty acylation sites. Fatty acylation of HHL subunits was analyzed by site-directed mutagenesis. Metabolic labeling of Cos7 cells transfected with wild type HHL1 cDNA resulted in substantial incorporation of [3H]palmitate into purified HHL1. Incorporation of [3H]palmitate into a C36S mutant of HHL1 was negligible ( approximately 1%) compared with wild type. This result also shows that Cys57 within the transmembrane domain of HHL1 is not normally palmitoylated. We conclude that Cys35 in RHL1, Cys54 in RHL2 and RHL3, and Cys36 in HHL1 are fatty acylated. Cys57 in HHL1 and probably Cys56 in RHL1 are not palmitoylated.
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PMID:Fatty acylation of the rat and human asialoglycoprotein receptors. A conserved cytoplasmic cysteine residue is acylated in all receptor subunits. 894 11